Process for producing butadiene



Patented Au 26, 1947 PROCESS FOR PRODUCING BUTADIENE William J. Hale,Midland, Mich, and Harry Miller, Columbia, Mo., assignors, by direct andmesne assignments, to National Agrol Com- 7 pany, Inc., Washington, D.(1., a corporation of Delaware No Drawing. Application February 22,1943, Serial No. 476,758

16 Claims. (01. zoo-cs1) This invention relates to a method fordehydrating and more particularly to dealcoholating and to a method offorming butadiene through the agency of a dehydrative catalyst.

This application is a continuation-in-part of our copending applicationSerial Number 465,391, filed November 12, 1942.

Among the objects of this invention may be noted the provision of amethod for dehydration; the provision of a method of the type indicatedwhich provides improved yields of 1,3-butadiene; the provision ofdehydration methods which form 1,3-butadiene without the formation ofsubstantial proportions of unwanted by-products; and the provision ofmethods of the type referred to which leave unreacted components in aform suitable for use in the present invention. Other objects will be inpart apparent and in part pointed out hereinafter.

The invention accordingly comprises the ingredients and combinations ofingredients, the

proportions thereof, steps and sequence of steps, and features ofcomposition and synthesis, analysis, or metathesis, which will beexemplified in the products and processes hereinafter described, and thescope of the application of which will be indicated in the followingclaims. I

In our earlier application, Serial Number 465,391, we have describedfully the course of various reactions involved when an alcohol reactswith an aldehyde and when the resulting acetal is subjected to adehydrative catalyst in the presence of ethylene. It has beenrecommended that the dealcoholated diethyl acetal, known as vinyl ethylether, might well be mixed with an incoming portion of the diethylacetal itself to constitute a preferred feed to the system for reactionwith the ethylene. In the light of recent discoveries we now choose tomodify this general procedure to obtain a higher conversion into1,3-butadiene per pass with much smaller proportions of impurities.

When'operating under the influence of a particularly active dehydrative(hydrative) catalyst there is the possibility that when acetals arepresent a certain portion of the alcohol liberated in the dealcoholationof the acetal, might be dehydrated to an ether and'water, or to anolefine and water if the alcohol has at least a two carbon atom chain.

We have now found that under the conditions of operation accompanyinguse of an active dehydrative catalyst it is not advisable to raise thetemperature above approximately 200-205 C.

when reacting ethylene with, for example, diethyl acetal and itsdealcoholated form, vinyl ethyl ether. Otherwise the effect of anincreased amount of moisture tends to vitiate the results. As soon aswater appears in the system there is the possibility of hydrolysis ofthe acetal itself into acetaldehyde and'alcohol as well as of the vinylethyl ether into vinyl alcohol and ethyl alcohol. Also there is thepossibility of condensations of the aldehyde, as well as a series ofcom-' plicated reactions of the butadiene with water. As little as /4 ofone per cent of water is deleterious. i I

1,3-butadiene is stable in the presence of water but under the influenceof active dehydrative (hydrative) catalysts, it reacts to give the an-,

hydride of 2,3-butylene glycol CHaOHCH-CHa O which immediatelyrearranges into methyl ethyl ketone (CH3CO-C2H5). A further undesirableproduct formed in lesser amount is butyric aldehyde (CH3CH2-CH2CHO)which is formed by the complete dehydration of the acetyl group ofmethyl ethyl ketone and rehydration of the same in reverse order. Thesetwo impurities are present in something approaching a total of 10% byweight of the butadiene formed by one pass over an especially activedehydrative catalyst such as a mixture of freshly precipitated aluminumoxide and the blue oxide of tungsten at as low a temperature as C. Moredetrimental, of course, is the tendency of butadiene to' hydrate whenthe temperature approaches 230 250 C. especially under increasedpressure. This is the reason why processes for the com mercialmanufacture of butadiene which start with ethyl alcohol or acetaldehydeor mixtures of the two and are carried out at temperatures above 250 C.are accompanied by extraordinarily low yields of butadiene, even thoughat high temperatures methyl ethyl ketone itself may be made to formbutadiene. In all the yield of butadiene in these so-called crackingprocesses does not exceed about 2.2 lbs. per gallon of original ethylalcohol, whereas the theoretical yield from a gallon of ethyl alcohol is3.86 lbs of butadiene. By the procedure of this invention we haveobtained as high as 3.2 lbs. of butadiene. calculated ,per gallon oforiginal alcohol.

According to the present invention the conversion of ethyl alcohol oracetaldehyde'or compounds thereof into 1,3-butadiene is carried outunder completely anhydrous conditions. When operating with diethylacetal (CH3CH(OC2H5)2) and ethylene, the first stage of thedealcoholation through vinyl ethyl ether (CH2=CHOC2H5) and ethyl alcoholproceeds well and the ethylene in turn reacts with the vinyl ethyl etherto yield butadiene and ethyl alcohol, but at even as low a temperatureas 220 C. a certainamount'of this free ethyl alcohol suffereddehydration. This lowered the yield of butadiene, so it was in generalconsidered most desirable to conduct this reaction at as low atemperature as 185-l90 C., where however the speed of reaction ismaterially reduced.

We have now discovered that complete removal of the danger of olefineand water formation in the course of the passage of acetals overdehydrative catalysts is effected by choosing an alcohol inherentlyincapable of yielding an olefine by dehydration, such, for example, asmethyl alcohol or its aryl derivative benzyl alcohol. In this way weutilize as starting materials dimethyl acetal (CH3CH(OCH3)2) anddibenzyl acetal which respectively yield upon dealcoholation vinylmethyl ether (CH2=CHOCH3) and. vinyl benzyl ether (CH2=CHO--CH2-CeH5).We have therefore only to guard against dehydration of these alcoholsinto their respective ethers in order to eliminate completely thepossibility of water formation in the system. This latter condition isobtained by operating with the dimethyl acetal and vinyl methyl ether,below 250 C., the temperature at which wate;- begins to form through thedehydration of methyl alcohol in the presence of active aluminum oxides,Preferably a maximum temperature of 230 should not be exceeded in theuse of catalysts containing certain other well known dehydrative oxidessuch as titanium oxide, zirconium oxide and molybdic .oxide whichactsomewhat dehydrogenatively on methyl alcohol. The preferred feed to asystem operating with ethylene in the production of buta diene may hereagain be chosen as a mixture of the acetal in question, dimethyl ordibenzyl acetals, and their dealcoholatecl forms, that is,

the vinyl alkyl or vinyl aryl ether. The free alcohol which separatesout in the first step following the reaction chamber may be brought intoreaction with a second portion of acetaldehyde for recycling through thesystem.

With reference to the more or less unsatisfactory conditions thatsometimes prevail where diethyl acetal and ethylene are made to reactover an active dehydrative catalyst, we have now discovered that in thepresence of such a catalyst especially if it has a dehydrogenativecomponent, the ethyl alcohol liberated actually begins to sufferdehydration at as low a temperature as 240 0., approximately ,below thecorresponding point for methyl alcohol. Hence the use of diethyl acetalrequires operation at lower temperatures than dimethyl acetal.

We have now discovered that the dealcoholation of dimethyl acetal tovinyl methyl ether and the dealcoholation of dibenzyl acetal into vinylbenzyl ether proceeds with great ease and that the subsequentinteraction of ethylene upon these ethers is more or less dependent uponthe ready dissociation of the ethylene. Generally speaking, at 200-205C. vinyl methyl ether and ethylene in the presence of any gooddehydrative, dehydrogenative catalyst will show a 80% conversion intobutadiene in one pass. The presence of the dehydrogenative component inthe catalyst materially aids the reaction of ethylene with the ether.Among the dehydrogenative agents that may serve this purpose may-bementioned the walls of the reaction chamber especially if it is composed'of copper. Furthermore, the presence of silver, gold and mercury allcontribute to the coupling reaction involved. The walls of the tube(reaction vessel) may be of any of the noble or near-noble metals,except mercury, which functions in the'manner stated.

In this connection it has further been discovered thata small trace of.a tertiary amine or of an amino organic base such as pyridine orquinoline, when added to the incoming mixture of vinyl alkyl or vinylaryl ether and ethylene, contributes markedly to the speed of thereaction and hence leads to a greater percentage conversion intobutadiene.

We have also discovered that the use of increased pressure contributesmost favorably to the reaction between vinyl alkyl or vinyl aryl ethersand ethylene. From 3 to 4, atmospheres is found highly favorablealthough as much as 50 atmospheres has been found to be useful when,

proceed at a rapid rate at C. No water is formed since the catalyst isnot efiective to dehydrate ethyl alcohol under these conditions.

In our preferred method for producing butadiene from acetals and their.dealc'oholated forms, it is first necessary to prepare the acetal in asnearly pure condition as possible. A mixture of 2 /2 mols of methylalcohol and 1 mol of acetaldehyde is allowed to stand overnight in thepresence of a condensing agent such as zinc chloride or other well knowncondensing agents. The layer of acetal and excess alcohol is thenremoved and thoroughly dried over a drying agent and carefullyfractionated using precautions to select a fraction practically free ofacetaldehyde. The preparation of dibenzyl acetal is carried out in asimilar manner.

The following examples illustrate the invention.

' Example 1 Into a glass combustion tube of internal bore with a lengthof 16" there was placed 100 g. of a freshly prepared mixture of aluminumoxide and blue oxide of tungsten in the form of 20 mesh pellets. Thisoccupied about 8" of the total tube length. The temperature of thecatalyst was then brought to -205" C. and a mixture of an excess ofethylene with 58 g. of vinyl methyl ether was passedthrough it in thecourse of thirty minutes, The yield of butadiene was 14.3 g. or 26.4% oftheoretical.

Example 2 Into a copper combustion tube of internal bore with a lengthof 16 there was placed 100 g. of a freshly prepared mixture of aluminumoxide and blue oxide of tungsten in the form of 2 0 mesh pellets. Itoccupied about 8 of the total tube length. The temperature of the catanexcess of ethylene was passed through the tube .during the course ofthirty minutes. The first condensate obtained with ice water consistedof methyl alcohol. The second condensate obtained by Dry Ice cooling to,2 C. consisted of unacted upon vinyl methyl ether (about 39 g.). The

butadiene was collected. over a gasometer with' the ethylene. Thebutadiene weighed 17.7 g. calculating to 32.8% of theoretical.-

Example 3 Example 2 was repeated in all respects except that thecatalyst was" made up ofv dehydrative and dehydrogenative agents. Itconsisted of 60 parts of freshly prepared aluminum oxide, 20 parts ofblue oxide of tungsten, parts of molybdenum oxide and 10 parts ofmetallic silver. Also the temperature was raised to 210-215 C. and thefeed current was heated to approximately the same temperature. The yieldof butadiene amounted to 21 g., calculating to 38.8% of theoretical. i fv Example 4 Example 3 was repeated in all respects except that the feedof 58 g. of vinyl methyl ether and .an excess of ethylene contained twodrops of quinoline. The yield of butadiene amounted to 28 g. calculatingto 51.8% of theoretical,

Example 5 Example 4 was repeated inall respects except that a few dropsof trimethyl amine weresubstituted for the quinoline. The yield wasapproximately the same as in Example 4.

Example 6 Example 4 was repeated in all respects except that the systemwas placed under 4 atmospheres of pressure. The yield rose to 35.4 g. ofbutadien e, calculating to 65.5% of theoretical.

Example .7

Example 3 was repeated but this time at a tem-,

Example 8 I Into a steel bomb of 100 ml. volume, 5 g. of ,vinyl ethylether was introduced with 5 g. of liquid ethylene and a catalyst ofaluminum oxide, chromium oxide, tungsten oxide and copper. About 80% ofthe catalyst consisted of themixed oxides and of copper. The bomb washeated to 125 C. whereby a pressure of 600 lbs. was developed. Afterhalf an hour the bomb was opened and-the reaction to butadiene was foundto be about 50% complete.

By anhydrous we mean a water content of less than approximately of 1%.

In view of the above, it will be seen that the several objects of the.invention are achieved and other advantageous results attained.

As many changes could be made in the above processes and productswithout departing from the scope of the invention, it is intended thatall matter contained in the above description shall be interpreted asillustrative and not in a limiting sense.

. 6v We claim: 1. The method of making butadiene which comprisesreacting a substance selected from the group consisting of dimethylacetal, dibenzyl acetal, vinyl methyl ether and vinyl benzyl ether,

with ethylene. at temperatures under 250 C. and

in the presence of a selected dehydrative catalyst containing less than10% of its weight of a noble metal as a condensing agent which does notsplit off water from the liberated alcohol under the conditions of theoperation.

2. A method of producing butadiene which com prises, reacting dimethylacetal with ethylene, at temperatures below about 250 C. and in thepresence of'a dehydrative catalyst. under conditions which tend to avoidsplitting water from the liber ated alc'ohol. V I

3. A method of making butadiene which comprises, reacting dimethylacetal with ethylene, at temperatures below 250' C., in the presence ofa catalyst comprising a pre'ponderant amount of a dehydrative catalyticmaterial and a smaller amount of a condensing agent comprising a noblemetal.

4. A method of making butadiene which comprises, reacting dimethylacetal with ethylene, at temperatures below about 250 C., in thepresence of a dehydrative catalyst and a minor quantity of a tertiaryamine as a condensing agent.

5. A method of making butadiene which comprises, reacting dibenzylacetal with ethylene, at temperatures below about 250 C., in thepresence of a.- dehydrative catalyst under conditions which tend toliberate alcohol but which do not release water from the liberatedbenzyl alcohol.

e 6. A method of making butadiene which comprises, reacting dibenzylacetal with ethylene, at

temperatures below about 250 C., in the presence of a selecteddehydrative catalyst under conditions which tend to liberate alcohol butwhich do not liberate water from the formed benzyl alcohol, saidcatalyst containing a minor amount of-a condensing agent comprised of anoble metal.

7. A method of producing butadiene which comprises, reacting dibenzylacetal with ethylene, at temperatures below about 250 C., in thepresence of a dehydrative catalyst and "in the presence of aminorquantity of the vapors of a tertiary amine.

- 8. A method of producing butadiene which comprises, reacting vinylmethyl ether with ethylene, at temperatures below about 250 C., in thepresence of a selected dehydrative catalyst which tends to liberatemethyl alcohol, the conditions being such as to inhibit the dehydrationof the liberated alcohol.

9. A method of making butadiene which comprises, reacting vinyl methylether with ethylene, at temperatures below about 250 C., in the presenceof a catalytic material comprising a preponderant amount of a,dehydrative catalyst incapable of dehydrating methyl alcohol, -saidcatalyst containing a minor amount of a noble metal as a condensingagent.

10. A method of producing butadiene which comprises, reacting vinylmethyl ether with ethylene, at temperatures below about 250 C., in thepresence of a small quantity of a tertiary amine and a selecteddehydrative catalyst which tends to liberate methyl alcohol but whichdoes not dehydrate the liberated methyl alcohol under the conditions ofthe reaction.

11. A process of producing butadiene which peratures belowabout 250 C.and in the presence of a selected dehydrative catalyst which tends toliberate methyl alcohol but which does not dehydrate the liberatedmethyl alcohol under the conditions of the operation.

12.'A method of producing butadiene which comprises, reacting vinylmethyl ether and dimethyl acetal with ethylene at temperatures belowabout 250 C. and in the presence of a catalytic mass comprising apreponderant amount of a dehydrated catalyst which tends to liberatemethyl alcohol but which does not dehydrate the liberated methyl alcoholand a minor amount of I a noble metal.

13. A method of producing butadiene which comprises, reacting vinylmethyl ether and dimethyl acetal with ethylene, at temperatures belowabout 250 C., in the presence of the vapors of a tertiary amine and incontact with a selected dehydrative catalyst which tends to liberatemethyl alcohol but which-does not dehydrate the liberated methyl alcoholunder the conditions of the operation.

14. The process of making butadiene which comprises, reacting vinylbenzyl ether and dibenzyl acetal with ethylene, at temperatures belowabout 250 C., and in the presence of a selected dehydrative catalystwhich tend to liberate benzyl alcohol but which does not dehydrate theliberated benzyl alcohol.

15. .A process according to claim 14 in which the dehydrative catalystcontains approximately 10% of a noble metal 1 16. A process according toclaim 14 in which the reaction mixture contains a minute quantity of atertiary amine as a condensing agent.

WILLIAM J. HALE. HARRY MILLER.

REFERENCES CITED The following references are of record in the 10 fileof this patent:

UNITED STATES EATENTS 5 Dec. 1'7, 1942.

OTHER REFERENCES Ostromysslenski, J. Soc. Chem. Ind, 35, No. 1, pages69-70 (1916).

Eglofi et al., Oil and Gas Jour., pages 36-37,

Whitmore, Organic Chemistry," page 239, Van Nostrand, 1937.

Ostromysslenski et al., J. Russ. Phys. Chem.,

46, pages 123-33 (1914).

Talalay et al., Rubber Chemistry and Technology, 15, pages 424-5 (1942).Entire article extends from page 403 to 429, but only pages 424-5 areconsidered to be of interest.

